The present invention relates to an improvement in the method for the preparation of a high-strength fine wire of high-carbon steel by repeating patenting and cold-drawing. More particularly, the invention relates to an improvement in the method for the preparation of a high-strength fine wire of high-carbon steel having a diameter, for example, not exceeding 50 .mu.m and useful as a base material of tire cord wires, conveyor belt wires, high pressure-hose reinforcing wires, wire saws, mesh filters, precision springs and the like.
Very fine steel wires having a diameter of 100 .mu.m or smaller are manufactured usually by repeatedly subjecting a starting hot-drawn wire rod having a diameter of, for example, 5.5 mm to cold drawing and patenting treatment in a non-oxidizing atmosphere successively reducing the diameter or cross section of the wire in each cold drawing. It is generally understood in the prior art that the above mentioned wire-drawing process is not applicable to the manufacture of a high-carbon steel wire having a diameter of 50 .mu.m or smaller which should have a very high tensile strength of 300 to 800 kgf/mm.sup.2. The high-carbon steel here implied includes steels of those grades such as SWRS82A specified in JIS G 3507 which contains 0.51 to 0.86% by weight of carbon, 0.35% by weight or less of silicon and 0.5% by weight or less of manganese. Namely, a steel wire having a diameter of 100 to 200 .mu.m after cold drawing in a working degree, i.e. reduction of cross section, of 90 to 96% is already in a state of overworking so that no further cold drawing can be undertaken thereof without subjecting the wire to another patenting treatment. Nevertheless, a patenting treatment of such a fine steel wire can practically no longer be undertaken due to the problems of surface oxidation, spontaneous leaning and the like if not to mention breaking of the wire by a pickling treatment with a diluted acid solution.